[PATCH 58/71] xfs: garbage collect old cowextsz reservations

[Christoph Hellwig]

On Thu, Aug 25, 2016 at 04:38:14PM -0700, Darrick J. Wong wrote:
> Trim CoW reservations made on behalf of a cowextsz hint if they get too
> old or we run low on quota, so long as we don't have dirty data awaiting
> writeback or directio operations in progress.

FYI, at least in your latest tree we only ever seem to set
xfs_inode_set_cowblocks_tag in xfs_swap_extents, so this effectively
isn't used during normal fs usage.

Also any reason we can't use the same infrastructure as our normal
speculative preallocation here?